Centrifugal compressors rotating at high speed are known, and in these a mechanical speed multiplier is located between an electric drive motor and the shaft which drives the wheel or wheels of the compressor. In these known compressors, a flexible clutch, called a low-speed clutch, is located between the rotor of the electric motor and the input wheel of the multiplier, and another flexible clutch, called a high-speed clutch, is located between the output pinion of the multiplier and the rotor of the compressor.
These known compressors have a number of disadvantages, including the following:
the multiplier and its associated clutches require costly lubrication arrangements with a high energy consumption;
the problem of critical speed is complex because of the multiplicity of the rotating parts;
because of the large number of parts, the reliability of the compression unit is not very high;
problems of alignment arise as a result of the presence of several moving parts;
since the compression unit is not compact, the various components are generally arranged on different bases and supports, and this has a disadvantageous effect on the cost of the whole system.